Fiber optic connectors are used to link various optical components, cable assemblies, transmission devices and testing equipment. To insure low loss and low reflective performance, a connector's precision ferrule, in which the fiber is mounted, must be polished to a scratch-free finish with demanding geometric criteria.
The ferrule tip of most high performance connectors is polished to a convex geometry. Ideally, the apex of the convex surface should coincide with the center axis of the fiber. The deviation from this ideal geometry is referred to as the connector's apex offset. Apex offset is created when the ferrule endface is not held perpendicular to the abrasive surface used during the polishing process. An interferometer is a commonly used test instrument that can measure apex offset through the analysis of interference patterns created by light reflected off of the ferrule and fiber endface.
Prior art has demonstrated that equipment has been developed to automatically polish connectors. These polishers utilize precisely machined workholders in which connectors are inserted. The workholder is then engaged with a support bracket and positioned so that the connector's ferrules are placed in contact with a rotating polishing surface. The degree of perpendicularity maintained between the ferrule axis and the polishing surface is highly dependent upon the polisher's mechanical assembly, machined parts' tolerances, and workholder/polisher engagement mechanism. These variables compound upon each other resulting in increased apex offset error.
Prior art also has a significant shortcoming regarding the control of apex offset. Most automated polishers are designed to support the simultaneous processing of a plurality of connectors. Hence the workholder is machined with a multitude of connector ports. There always exists a machining tolerance from port to port, a variable that will be reflected in differing apex offsets. These ports are fixed and cannot be adjusted for individual connectors.
An additional shortcoming of prior art is the method in which connectors are secured within the workholder. Connectors are slip fitted into bushings or sleeves and locked into position. Because of dimensional tolerance differences between the outer diameter of the connector ferrule and the inner diameter of the bushing/sleeve, the locking means tilts the ferrule creating additional apex offset.
A further shortcoming of prior art is that polisher workholders are machined and mechanically assembled. The connector orientation cannot be adjusted with an interferometric reference. Therefore the workholder cannot be utilized for in-line interferometric inspection of connectors that are secured in the workholder.